Mailing List Archive

We provide a new set of functions and related structures
libxl_osevent_*
which are to be used by event-driven applications to receive
information from libxl about which fds libxl is interested in, and
what timeouts libxl is waiting for, and to pass back to libxl
information about which fds are readable/writeable etc., and which
timeouts have occurred. Ie, low-level events.

In this patch, this new machinery is still all unused. Callers will
appear in the next patch in the series, which introduces a new API for
applications to receive high-level events about actual domains etc.

Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
---
tools/libxl/Makefile | 2 +-
tools/libxl/libxl.c | 25 ++
tools/libxl/libxl.h | 6 +
tools/libxl/libxl_event.c | 711 ++++++++++++++++++++++++++++++++++++++++++
tools/libxl/libxl_event.h | 199 ++++++++++++
tools/libxl/libxl_internal.h | 216 +++++++++++++-
6 files changed, 1155 insertions(+), 4 deletions(-)
create mode 100644 tools/libxl/libxl_event.c
create mode 100644 tools/libxl/libxl_event.h

diff --git a/tools/libxl/Makefile b/tools/libxl/Makefile
index 4e0f3fb..3d575b8 100644
--- a/tools/libxl/Makefile
+++ b/tools/libxl/Makefile
@@ -38,7 +38,7 @@ LIBXL_LIBS += -lyajl
LIBXL_OBJS = flexarray.o libxl.o libxl_create.o libxl_dm.o libxl_pci.o \
libxl_dom.o libxl_exec.o libxl_xshelp.o libxl_device.o \
libxl_internal.o libxl_utils.o libxl_uuid.o libxl_json.o \
- libxl_qmp.o $(LIBXL_OBJS-y)
+ libxl_qmp.o libxl_event.o $(LIBXL_OBJS-y)
LIBXL_OBJS += _libxl_types.o libxl_flask.o _libxl_types_internal.o

$(LIBXL_OBJS): CFLAGS += $(CFLAGS_libxenctrl) $(CFLAGS_libxenguest) $(CFLAGS_libxenstore) $(CFLAGS_libblktapctl)
diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 3a8cfe3..58f280c 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -60,6 +60,16 @@ int libxl_ctx_alloc(libxl_ctx **pctx, int version,
* only as an initialiser, not as an expression. */
memcpy(&ctx->lock, &mutex_value, sizeof(ctx->lock));

+ ctx->osevent_hooks = 0;
+
+ ctx->fd_beforepolled = 0;
+ LIBXL_LIST_INIT(&ctx->efds);
+ LIBXL_TAILQ_INIT(&ctx->etimes);
+
+ ctx->watch_slots = 0;
+ LIBXL_SLIST_INIT(&ctx->watch_freeslots);
+ libxl__ev_fd_init(&ctx->watch_efd);
+
if ( stat(XENSTORE_PID_FILE, &stat_buf) != 0 ) {
LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, "Is xenstore daemon running?\n"
"failed to stat %s", XENSTORE_PID_FILE);
@@ -89,10 +99,25 @@ int libxl_ctx_alloc(libxl_ctx **pctx, int version,

int libxl_ctx_free(libxl_ctx *ctx)
{
+ int i;
+ GC_INIT(ctx);
+
if (!ctx) return 0;
+
+ for (i = 0; i < ctx->watch_nslots; i++)
+ assert(!libxl__watch_slot_contents(gc, i));
+ libxl__ev_fd_deregister(gc, &ctx->watch_efd);
+
+ assert(LIBXL_LIST_EMPTY(&ctx->efds));
+ assert(LIBXL_TAILQ_EMPTY(&ctx->etimes));
+
if (ctx->xch) xc_interface_close(ctx->xch);
libxl_version_info_dispose(&ctx->version_info);
if (ctx->xsh) xs_daemon_close(ctx->xsh);
+
+ free(ctx->fd_beforepolled);
+ free(ctx->watch_slots);
+
return 0;
}

diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index 289dc85..654a5b0 100644
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -137,6 +137,7 @@
#include <xen/sysctl.h>

#include <libxl_uuid.h>
+#include <_libxl_list.h>

typedef uint8_t libxl_mac[6];
#define LIBXL_MAC_FMT "%02hhx:%02hhx:%02hhx:%02hhx:%02hhx:%02hhx"
@@ -222,6 +223,9 @@ enum {
ERROR_BADFAIL = -7,
ERROR_GUEST_TIMEDOUT = -8,
ERROR_TIMEDOUT = -9,
+ ERROR_NOT_READY = -10,
+ ERROR_OSEVENT_REG_FAIL = -11,
+ ERROR_BUFFERFULL = -12,
};

#define LIBXL_VERSION 0
@@ -635,6 +639,8 @@ const char *libxl_lock_dir_path(void);
const char *libxl_run_dir_path(void);
const char *libxl_xenpaging_dir_path(void);

+#include <libxl_event.h>
+
#endif /* LIBXL_H */

/*
diff --git a/tools/libxl/libxl_event.c b/tools/libxl/libxl_event.c
new file mode 100644
index 0000000..8d4dbf6
--- /dev/null
+++ b/tools/libxl/libxl_event.c
@@ -0,0 +1,711 @@
+/*
+ * Copyright (C) 2011 Citrix Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; version 2.1 only. with the special
+ * exception on linking described in file LICENSE.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ */
+/*
+ * Internal event machinery for use by other parts of libxl
+ */
+
+#include <poll.h>
+
+#include "libxl_internal.h"
+
+/*
+ * The counter osevent_in_hook is used to ensure that the application
+ * honours the reentrancy restriction documented in libxl_event.h.
+ *
+ * The application's registration hooks should be called ONLY via
+ * these macros, with the ctx locked. Likewise all the "occurred"
+ * entrypoints from the application should assert(!in_hook);
+ */
+#define OSEVENT_HOOK_INTERN(defval, hookname, ...) \
+ (CTX->osevent_hooks \
+ ? (CTX->osevent_in_hook++, \
+ CTX->osevent_hooks->hookname(CTX->osevent_user, __VA_ARGS__), \
+ CTX->osevent_in_hook--) \
+ : defval)
+
+#define OSEVENT_HOOK(hookname,...) \
+ OSEVENT_HOOK_INTERN(0, hookname, __VA_ARGS__)
+
+#define OSEVENT_HOOK_VOID(hookname,...) \
+ OSEVENT_HOOK_INTERN((void)0, hookname, __VA_ARGS__)
+
+/*
+ * fd events
+ */
+
+int libxl__ev_fd_register(libxl__gc *gc, libxl__ev_fd *ev,
+ libxl__ev_fd_callback *func,
+ int fd, short events) {
+ int rc;
+
+ assert(fd >= 0);
+
+ CTX_LOCK;
+
+ rc = OSEVENT_HOOK(fd_register, fd, &ev->for_app_reg, events, ev);
+ if (rc) goto out;
+
+ LIBXL_LIST_INSERT_HEAD(&CTX->efds, ev, entry);
+
+ ev->fd = fd;
+ ev->events = events;
+ ev->in_beforepolled = -1;
+ ev->func = func;
+
+ rc = 0;
+
+ out:
+ CTX_UNLOCK;
+ return rc;
+}
+
+int libxl__ev_fd_modify(libxl__gc *gc, libxl__ev_fd *ev, short events) {
+ int rc;
+
+ CTX_LOCK;
+ assert(libxl__ev_fd_isregistered(ev));
+
+ rc = OSEVENT_HOOK(fd_modify, ev->fd, &ev->for_app_reg, events);
+ if (rc) goto out;
+
+ ev->events = events;
+
+ rc = 0;
+ out:
+ CTX_UNLOCK;
+ return rc;
+}
+
+void libxl__ev_fd_deregister(libxl__gc *gc, libxl__ev_fd *ev) {
+ CTX_LOCK;
+
+ if (!libxl__ev_fd_isregistered(ev))
+ goto out;
+
+ OSEVENT_HOOK_VOID(fd_deregister, ev->fd, ev->for_app_reg);
+ LIBXL_LIST_REMOVE(ev, entry);
+ ev->fd = -1;
+
+ if (ev->in_beforepolled >= 0 &&
+ ev->in_beforepolled < CTX->fd_beforepolled_used)
+ /* remove stale reference */
+ CTX->fd_beforepolled[ev->in_beforepolled] = NULL;
+
+ out:
+ CTX_UNLOCK;
+}
+
+/*
+ * timeouts
+ */
+
+
+int libxl__gettimeofday(libxl__gc *gc, struct timeval *now_r) {
+ int rc = gettimeofday(now_r, 0);
+ if (rc) {
+ LIBXL__LOG_ERRNO(CTX, LIBXL__LOG_ERROR, "gettimeofday failed");
+ return ERROR_FAIL;
+ }
+ return 0;
+}
+
+static int time_rel_to_abs(libxl__gc *gc, int ms, struct timeval *abs_out) {
+ int rc;
+ struct timeval additional = {
+ .tv_sec = ms / 1000,
+ .tv_usec = (ms % 1000) * 1000
+ };
+ struct timeval now;
+
+ rc = libxl__gettimeofday(gc, &now);
+ if (rc) return rc;
+
+ timeradd(&now, &additional, abs_out);
+ return 0;
+}
+
+static void time_insert_finite(libxl__gc *gc, libxl__ev_time *ev) {
+ libxl__ev_time *evsearch;
+ LIBXL_TAILQ_INSERT_SORTED(&CTX->etimes, entry, ev, evsearch, ,
+ timercmp(&ev->abs, &evsearch->abs, >));
+ ev->infinite = 0;
+}
+
+static int time_register_finite(libxl__gc *gc, libxl__ev_time *ev,
+ struct timeval abs) {
+ int rc;
+
+ rc = OSEVENT_HOOK(timeout_register, &ev->for_app_reg, abs, ev);
+ if (rc) return rc;
+
+ ev->infinite = 0;
+ ev->abs = abs;
+ time_insert_finite(gc, ev);
+
+ return 0;
+}
+
+static void time_deregister(libxl__gc *gc, libxl__ev_time *ev) {
+ if (!ev->infinite) {
+ OSEVENT_HOOK_VOID(timeout_deregister, &ev->for_app_reg);
+ LIBXL_TAILQ_REMOVE(&CTX->etimes, ev, entry);
+ }
+}
+
+
+int libxl__ev_time_register_abs(libxl__gc *gc, libxl__ev_time *ev,
+ libxl__ev_time_callback *func,
+ struct timeval abs) {
+ int rc;
+
+ CTX_LOCK;
+
+ rc = time_register_finite(gc, ev, abs);
+ if (rc) goto out;
+
+ ev->func = func;
+
+ rc = 0;
+ out:
+ CTX_UNLOCK;
+ return rc;
+}
+
+
+int libxl__ev_time_register_rel(libxl__gc *gc, libxl__ev_time *ev,
+ libxl__ev_time_callback *func,
+ int milliseconds /* as for poll(2) */) {
+ struct timeval abs;
+ int rc;
+
+ CTX_LOCK;
+
+ if (milliseconds < 0) {
+ ev->infinite = 1;
+ } else {
+ rc = time_rel_to_abs(gc, milliseconds, &abs);
+ if (rc) goto out;
+
+ rc = time_register_finite(gc, ev, abs);
+ if (rc) goto out;
+ }
+
+ ev->func = func;
+ rc = 0;
+
+ out:
+ CTX_UNLOCK;
+ return 0;
+}
+
+int libxl__ev_time_modify_abs(libxl__gc *gc, libxl__ev_time *ev,
+ struct timeval abs) {
+ int rc;
+
+ CTX_LOCK;
+
+ assert(libxl__ev_time_isregistered(ev));
+
+ if (ev->infinite) {
+ rc = time_register_finite(gc, ev, abs);
+ if (rc) goto out;
+ } else {
+ rc = OSEVENT_HOOK(timeout_modify, &ev->for_app_reg, abs);
+ if (rc) goto out;
+
+ LIBXL_TAILQ_REMOVE(&CTX->etimes, ev, entry);
+ ev->abs = abs;
+ time_insert_finite(gc, ev);
+ }
+
+ rc = 0;
+ out:
+ CTX_UNLOCK;
+ return rc;
+}
+
+int libxl__ev_time_modify_rel(libxl__gc *gc, libxl__ev_time *ev,
+ int milliseconds) {
+ struct timeval abs;
+ int rc;
+
+ CTX_LOCK;
+
+ assert(libxl__ev_time_isregistered(ev));
+
+ if (milliseconds < 0) {
+ time_deregister(gc, ev);
+ ev->infinite = 1;
+ rc = 0;
+ goto out;
+ }
+
+ rc = time_rel_to_abs(gc, milliseconds, &abs);
+ if (rc) goto out;
+
+ rc = libxl__ev_time_modify_abs(gc, ev, abs);
+ if (rc) goto out;
+
+ rc = 0;
+ out:
+ CTX_UNLOCK;
+ return 0;
+}
+
+void libxl__ev_time_deregister(libxl__gc *gc, libxl__ev_time *ev) {
+ CTX_LOCK;
+
+ if (!libxl__ev_time_isregistered(ev))
+ goto out;
+
+ time_deregister(gc, ev);
+ ev->func = 0;
+
+ out:
+ CTX_UNLOCK;
+ return;
+}
+
+
+/*
+ * xenstore watches
+ */
+
+libxl__ev_xswatch *libxl__watch_slot_contents(libxl__gc *gc, int slotnum) {
+ libxl__ev_watch_slot *slot = &CTX->watch_slots[slotnum];
+ libxl__ev_watch_slot *slotcontents = LIBXL_SLIST_NEXT(slot, empty);
+
+ if (slotcontents == NULL ||
+ ((uintptr_t)slotcontents >= (uintptr_t)CTX->watch_slots &&
+ (uintptr_t)slotcontents < (uintptr_t)(CTX->watch_slots +
+ CTX->watch_nslots)))
+ /* An empty slot has either a NULL pointer (end of the
+ * free list), or a pointer to another entry in the array.
+ * So we can do a bounds check to distinguish empty from
+ * full slots.
+ */
+ /* We need to do the comparisons as uintptr_t because
+ * comparing pointers which are not in the same object is
+ * undefined behaviour; if the compiler managed to figure
+ * out that watch_slots[0..watch_nslots-1] is all of the
+ * whole array object it could prove that the above bounds
+ * check was always true if it was legal, and remove it!
+ *
+ * uintptr_t because even on a machine with signed
+ * pointers, objects do not cross zero; whereas on
+ * machines with unsigned pointers, they may cross
+ * 0x8bazillion.
+ */
+ return NULL;
+
+ /* see comment near libxl__ev_watch_slot definition */
+ return (void*)slotcontents;
+}
+
+static void watchfd_callback(libxl__gc *gc, libxl__ev_fd *ev,
+ int fd, short events, short revents) {
+ for (;;) {
+ char **event = xs_check_watch(CTX->xsh);
+ if (!event) {
+ if (errno == EAGAIN) break;
+ if (errno == EINTR) continue;
+ LIBXL__EVENT_DISASTER(gc, "cannot check/read watches", errno, 0);
+ return;
+ }
+
+ const char *epath = event[0];
+ const char *token = event[1];
+ int slotnum;
+ uint32_t counterval;
+ int rc = sscanf(token, "%d/%"SCNx32, &slotnum, &counterval);
+ if (rc != 2) {
+ LIBXL__LOG(CTX, LIBXL__LOG_ERROR,
+ "watch epath=%s token=%s: failed to parse token",
+ epath, token);
+ /* oh well */
+ goto ignore;
+ }
+ if (slotnum < 0 || slotnum >= CTX->watch_nslots) {
+ /* perhaps in the future we will make the watchslots array shrink */
+ LIBXL__LOG(CTX, LIBXL__LOG_DEBUG, "watch epath=%s token=%s:"
+ " slotnum %d out of range [.0,%d>",
+ epath, token, slotnum, CTX->watch_nslots);
+ goto ignore;
+ }
+
+ libxl__ev_xswatch *w = libxl__watch_slot_contents(gc, slotnum);
+
+ if (!w) {
+ LIBXL__LOG(CTX, LIBXL__LOG_DEBUG,
+ "watch epath=%s token=%s: empty slot",
+ epath, token);
+ goto ignore;
+ }
+
+ if (w->counterval != counterval) {
+ LIBXL__LOG(CTX, LIBXL__LOG_DEBUG,
+ "watch epath=%s token=%s: counter != %"PRIx32,
+ epath, token, w->counterval);
+ goto ignore;
+ }
+
+ /* Now it's possible, though unlikely, that this was an event
+ * from a previous use of the same slot with the same counterval.
+ *
+ * In that case either:
+ * - the event path is a child of the watch path, in
+ * which case this watch would really have generated this
+ * event if it had been registered soon enough and we are
+ * OK to give this possibly-spurious event to the caller; or
+ * - it is not, in which case we must suppress it as the
+ * caller should not see events for unrelated paths.
+ *
+ * See also docs/misc/xenstore.txt.
+ */
+ size_t epathlen = strlen(epath);
+ size_t wpathlen = strlen(w->path);
+ if (epathlen < wpathlen ||
+ memcmp(epath, w->path, wpathlen) ||
+ (epathlen > wpathlen && epath[wpathlen] != '/')) {
+ LIBXL__LOG(CTX, LIBXL__LOG_DEBUG,
+ "watch epath=%s token=%s: not child of wpath=%s",
+ epath, token, w->path);
+ goto ignore;
+ }
+
+ /* At last, we have checked everything! */
+ LIBXL__LOG(CTX, LIBXL__LOG_DEBUG,
+ "watch event: epath=%s token=%s wpath=%s w=%p",
+ epath, token, w->path, w);
+ w->callback(gc, w, w->path, epath);
+
+ ignore:
+ free(event);
+ }
+}
+
+static char *watch_token(libxl__gc *gc, int slotnum, uint32_t counterval) {
+ return libxl__sprintf(gc, "%d/%"PRIx32, slotnum, counterval);
+}
+
+int libxl__ev_xswatch_register(libxl__gc *gc, libxl__ev_xswatch *w,
+ libxl__ev_xswatch_callback *func,
+ const char *path /* copied */) {
+ libxl__ev_watch_slot *use = NULL;
+ char *path_copy = NULL;
+ int rc;
+
+ CTX_LOCK;
+
+ if (!libxl__ev_fd_isregistered(&CTX->watch_efd)) {
+ rc = libxl__ev_fd_register(gc, &CTX->watch_efd, watchfd_callback,
+ xs_fileno(CTX->xsh), POLLIN);
+ if (rc) goto out_rc;
+ }
+
+ if (LIBXL_SLIST_EMPTY(&CTX->watch_freeslots)) {
+ /* Free list is empty so there is not in fact a linked
+ * free list in the array and we can safely realloc it */
+ int newarraysize = (CTX->watch_nslots + 1) << 2;
+ int i;
+ libxl__ev_watch_slot *newarray =
+ realloc(CTX->watch_slots, sizeof(*newarray) * newarraysize);
+ if (!newarray) goto out_nomem;
+ for (i=CTX->watch_nslots; i<newarraysize; i++)
+ LIBXL_SLIST_INSERT_HEAD(&CTX->watch_freeslots,
+ &newarray[i], empty);
+ CTX->watch_slots = newarray;
+ CTX->watch_nslots = newarraysize;
+ }
+ use = LIBXL_SLIST_FIRST(&CTX->watch_freeslots);
+ assert(use);
+ LIBXL_SLIST_REMOVE_HEAD(&CTX->watch_freeslots, empty);
+
+ path_copy = strdup(path);
+ if (!path_copy) goto out_nomem;
+
+ int slotnum = use - CTX->watch_slots;
+ w->counterval = CTX->watch_counter++;
+
+ if (!xs_watch(CTX->xsh, path, watch_token(gc, slotnum, w->counterval))) {
+ LIBXL__LOG_ERRNOVAL(CTX, LIBXL__LOG_ERROR, errno,
+ "create watch for path %s", path);
+ rc = ERROR_FAIL;
+ goto out_rc;
+ }
+
+ w->slotnum = slotnum;
+ w->path = path_copy;
+ w->callback = func;
+ /* we look a bit behind the curtain of LIBXL_SLIST, to explictly
+ * assign to the pointer that's the next link. See the comment
+ * by the definitionn of libxl__ev_watch_slot */
+ use->empty.sle_next = (void*)w;
+
+ CTX_UNLOCK;
+ return 0;
+
+ out_nomem:
+ rc = ERROR_NOMEM;
+ out_rc:
+ if (use)
+ LIBXL_SLIST_INSERT_HEAD(&CTX->watch_freeslots, use, empty);
+ if (path_copy)
+ free(path_copy);
+ CTX_UNLOCK;
+ return rc;
+}
+
+void libxl__ev_xswatch_deregister(libxl__gc *gc, libxl__ev_xswatch *w) {
+ /* it is legal to deregister from within _callback */
+ CTX_LOCK;
+
+ if (w->slotnum >= 0) {
+ char *token = watch_token(gc, w->slotnum, w->counterval);
+ if (!xs_unwatch(CTX->xsh, w->path, token))
+ /* Oh well, we will just get watch events forever more
+ * and ignore them. But we should complain to the log. */
+ LIBXL__LOG_ERRNOVAL(CTX, LIBXL__LOG_ERROR, errno,
+ "remove watch for path %s", w->path);
+
+ libxl__ev_watch_slot *slot = &CTX->watch_slots[w->slotnum];
+ LIBXL_SLIST_INSERT_HEAD(&CTX->watch_freeslots, slot, empty);
+ }
+
+ free(w->path);
+ w->path = NULL;
+
+ CTX_UNLOCK;
+}
+
+/*
+ * osevent poll
+ */
+
+int libxl_osevent_beforepoll(libxl_ctx *ctx, int *nfds_io,
+ struct pollfd *fds, int *timeout_upd,
+ struct timeval now) {
+ libxl__ev_fd *efd;
+ int i;
+
+ /*
+ * In order to be able to efficiently find the libxl__ev_fd
+ * for a struct poll during _afterpoll, we maintain a shadow
+ * data structure in CTX->fd_beforepolled: each slot in
+ * the fds array corresponds to a slot in fd_beforepolled.
+ */
+
+ GC_INIT(ctx);
+ CTX_LOCK;
+
+ if (*nfds_io) {
+ /*
+ * As an optimisation, we don't touch fd_beforepolled_used
+ * if *nfds_io is zero on entry, since in that case the
+ * caller just wanted to know how big an array to give us.
+ *
+ * If !*nfds_io, the unconditional parts below are guaranteed
+ * not to mess with fd_beforepolled... or any in_beforepolled.
+ */
+
+ /* Remove all the old references into beforepolled */
+ for (i = 0; i < CTX->fd_beforepolled_used; i++) {
+ efd = CTX->fd_beforepolled[i];
+ if (efd) {
+ assert(efd->in_beforepolled == i);
+ efd->in_beforepolled = -1;
+ CTX->fd_beforepolled[i] = NULL;
+ }
+ }
+ CTX->fd_beforepolled_used = 0;
+
+ /* make sure our array is as big as *nfds_io */
+ if (CTX->fd_beforepolled_allocd < *nfds_io) {
+ assert(*nfds_io < INT_MAX / sizeof(libxl__ev_fd*) / 2);
+ libxl__ev_fd **newarray =
+ realloc(CTX->fd_beforepolled, sizeof(*newarray) * *nfds_io);
+ if (!newarray)
+ return ERROR_NOMEM;
+ CTX->fd_beforepolled = newarray;
+ CTX->fd_beforepolled_allocd = *nfds_io;
+ }
+ }
+
+ int used = 0;
+ LIBXL_LIST_FOREACH(efd, &CTX->efds, entry) {
+ if (used < *nfds_io) {
+ fds[used].fd = efd->fd;
+ fds[used].events = efd->events;
+ fds[used].revents = 0;
+ CTX->fd_beforepolled[used] = efd;
+ efd->in_beforepolled = used;
+ }
+ used++;
+ }
+ int rc = used <= *nfds_io ? 0 : ERROR_BUFFERFULL;
+
+ if (*nfds_io) {
+ CTX->fd_beforepolled_used = used;
+ }
+
+ *nfds_io = used;
+
+ libxl__ev_time *etime = LIBXL_TAILQ_FIRST(&CTX->etimes);
+ if (etime) {
+ int our_timeout;
+ struct timeval rel;
+ static struct timeval zero;
+
+ timersub(&etime->abs, &now, &rel);
+
+ if (timercmp(&rel, &zero, <)) {
+ our_timeout = 0;
+ } else if (rel.tv_sec >= 2000000) {
+ our_timeout = 2000000000;
+ } else {
+ our_timeout = rel.tv_sec * 1000 + (rel.tv_usec + 999) / 1000;
+ }
+ if (*timeout_upd < 0 || our_timeout < *timeout_upd)
+ *timeout_upd = our_timeout;
+ }
+
+ CTX_UNLOCK;
+ GC_FREE;
+ return rc;
+}
+
+void libxl_osevent_afterpoll(libxl_ctx *ctx, int nfds, const struct pollfd *fds,
+ struct timeval now) {
+ int i;
+ GC_INIT(ctx);
+ CTX_LOCK;
+
+ assert(nfds <= CTX->fd_beforepolled_used);
+
+ for (i = 0; i < nfds; i++) {
+ if (!fds[i].revents)
+ continue;
+
+ libxl__ev_fd *efd = CTX->fd_beforepolled[i];
+ if (!efd)
+ continue;
+
+ assert(efd->in_beforepolled == i);
+ assert(fds[i].fd == efd->fd);
+
+ int revents = fds[i].revents & efd->events;
+ if (!revents)
+ continue;
+
+ efd->func(gc, efd, efd->fd, efd->events, revents);
+ }
+
+ for (;;) {
+ libxl__ev_time *etime = LIBXL_TAILQ_FIRST(&CTX->etimes);
+ if (!etime)
+ break;
+
+ assert(!etime->infinite);
+
+ if (timercmp(&etime->abs, &now, >))
+ break;
+
+ time_deregister(gc, etime);
+
+ etime->func(gc, etime, &etime->abs);
+ }
+
+ CTX_UNLOCK;
+ GC_FREE;
+}
+
+
+/*
+ * osevent hook and callback machinery
+ */
+
+void libxl_osevent_register_hooks(libxl_ctx *ctx,
+ const libxl_osevent_hooks *hooks,
+ void *user) {
+ GC_INIT(ctx);
+ CTX_LOCK;
+ ctx->osevent_hooks = hooks;
+ ctx->osevent_user = user;
+ CTX_UNLOCK;
+ GC_FREE;
+}
+
+
+void libxl_osevent_occurred_fd(libxl_ctx *ctx, void *for_libxl,
+ int fd, short events, short revents) {
+ libxl__ev_fd *ev = for_libxl;
+
+ GC_INIT(ctx);
+ CTX_LOCK;
+ assert(!CTX->osevent_in_hook);
+
+ assert(fd == ev->fd);
+ revents &= ev->events;
+ if (revents)
+ ev->func(gc, ev, fd, ev->events, revents);
+
+ CTX_UNLOCK;
+ GC_FREE;
+}
+
+void libxl_osevent_occurred_timeout(libxl_ctx *ctx, void *for_libxl) {
+ libxl__ev_time *ev = for_libxl;
+
+ GC_INIT(ctx);
+ CTX_LOCK;
+ assert(!CTX->osevent_in_hook);
+
+ assert(!ev->infinite);
+ LIBXL_TAILQ_REMOVE(&CTX->etimes, ev, entry);
+ ev->func(gc, ev, &ev->abs);
+
+ CTX_UNLOCK;
+ GC_FREE;
+}
+
+void libxl__event_disaster(libxl__gc *gc, const char *msg, int errnoval,
+ libxl_event_type type /* may be 0 */,
+ const char *file, int line, const char *func) {
+ libxl__log(CTX, XTL_CRITICAL, errnoval, file, line, func,
+ "DISASTER in event loop: %s%s%s%s",
+ msg,
+ type ? " (relates to event type " : "",
+ type ? libxl_event_type_to_string(type) : "",
+ type ? ")" : "");
+
+ /*
+ * FIXME: This should call the "disaster" hook supplied to
+ * libxl_event_register_callbacks, which will be introduced in the
+ * next patch.
+ */
+
+ const char verybad[] =
+ "DISASTER in event loop not handled by libxl application";
+ LIBXL__LOG(CTX, XTL_CRITICAL, verybad);
+ fprintf(stderr, "libxl: fatal error, exiting program: %s\n", verybad);
+ exit(-1);
+}
+
+/*
+ * Local variables:
+ * mode: C
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/tools/libxl/libxl_event.h b/tools/libxl/libxl_event.h
new file mode 100644
index 0000000..25efbdf
--- /dev/null
+++ b/tools/libxl/libxl_event.h
@@ -0,0 +1,199 @@
+/*
+ * Copyright (C) 2011 Citrix Ltd.
+ * Author Ian Jackson <ian.jackson@eu.citrix.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; version 2.1 only. with the special
+ * exception on linking described in file LICENSE.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ */
+
+#ifndef LIBXL_EVENT_H
+#define LIBXL_EVENT_H
+
+#include <libxl.h>
+
+
+/*======================================================================*/
+
+/*
+ * OS event handling - passing low-level OS events to libxl
+ *
+ * Event-driven programs must use these facilities to allow libxl
+ * to become aware of readability/writeability of file descriptors
+ * and the occurrence of timeouts.
+ *
+ * There are two approaches available. The first is appropriate for
+ * simple programs handling reasonably small numbers of domains:
+ *
+ * for (;;) {
+ * libxl_osevent_beforepoll(...)
+ * poll();
+ * libxl_osevent_afterpoll(...);
+ * for (;;) {
+ * r=libxl_event_check(...);
+ * if (r==LIBXL_NOT_READY) break;
+ * if (r) handle failure;
+ * do something with the event;
+ * }
+ * }
+ *
+ * The second approach uses libxl_osevent_register_hooks and is
+ * suitable for programs which are already using a callback-based
+ * event library.
+ *
+ * An application may freely mix the two styles of interaction.
+ */
+
+struct pollfd;
+
+int libxl_osevent_beforepoll(libxl_ctx *ctx, int *nfds_io,
+ struct pollfd *fds, int *timeout_upd,
+ struct timeval now);
+ /* The caller should provide beforepoll with some space for libxl's
+ * fds, and tell libxl how much space is available by setting *nfds_io.
+ * fds points to the start of this space (and fds may be a pointer into
+ * a larger array, for example, if the application has some fds of
+ * its own that it is interested in).
+ *
+ * On return *nfds_io will in any case have been updated by libxl
+ * according to how many fds libxl wants to poll on.
+ *
+ * If the space was sufficient, libxl fills in fds[0..<new
+ * *nfds_io>] suitably for poll(2), updates *timeout_upd if needed,
+ * and returns ok.
+ *
+ * If space was insufficient, fds[0..<old *nfds_io>] is undefined on
+ * return; *nfds_io on return will be greater than the value on
+ * entry; *timeout_upd may or may not have been updated; and
+ * libxl_osevent_beforepoll returns ERROR_BUFERFULL. In this case
+ * the application needs to make more space (enough space for
+ * *nfds_io struct pollfd) and then call beforepoll again, before
+ * entering poll(2). Typically this will involve calling realloc.
+ *
+ * The application may call beforepoll with fds==NULL and
+ * *nfds_io==0 in order to find out how much space is needed.
+ *
+ * *timeout_upd is as for poll(2): it's in milliseconds, and
+ * negative values mean no timeout (infinity).
+ * libxl_osevent_beforepoll will only reduce the timeout, naturally.
+ */
+void libxl_osevent_afterpoll(libxl_ctx *ctx, int nfds, const struct pollfd *fds,
+ struct timeval now);
+ /* nfds and fds[0..nfds] must be from the most recent call to
+ * _beforepoll, as modified by poll.
+ *
+ * This function actually performs all of the IO and other actions,
+ * and generates events (libxl_event), which are implied by either
+ * (a) the time of day or (b) both (i) the returned information from
+ * _beforepoll, and (ii) the results from poll specified in
+ * fds[0..nfds-1]. Generated events can then be retrieved by
+ * libxl_event_check.
+ */
+
+
+typedef struct libxl_osevent_hooks {
+ int (*fd_register)(void *user, int fd, void **for_app_registration_out,
+ short events, void *for_libxl);
+ int (*fd_modify)(void *user, int fd, void **for_app_registration_update,
+ short events);
+ void (*fd_deregister)(void *user, int fd, void *for_app_registration);
+ int (*timeout_register)(void *user, void **for_app_registration_out,
+ struct timeval abs, void *for_libxl);
+ int (*timeout_modify)(void *user, void **for_app_registration_update,
+ struct timeval abs);
+ void (*timeout_deregister)(void *user, void *for_app_registration_io);
+} libxl_osevent_hooks;
+
+void libxl_osevent_register_hooks(libxl_ctx *ctx,
+ const libxl_osevent_hooks *hooks,
+ void *user);
+ /* The application which calls register_fd_hooks promises to
+ * maintain a register of fds and timeouts that libxl is interested
+ * in, and make calls into libxl (libxl_osevent_occurred_*)
+ * when those fd events and timeouts occur. This is more efficient
+ * than _beforepoll/_afterpoll if there are many fds (which can
+ * happen if the same libxl application is managing many domains).
+ *
+ * For an fd event, events is as for poll(). register or modify may
+ * be called with events==0, in which case it must still work
+ * normally, just not generate any events.
+ *
+ * For a timeout event, milliseconds is as for poll().
+ * Specifically, negative values of milliseconds mean NO TIMEOUT.
+ * This is used by libxl to temporarily disable a timeout.
+ *
+ * If the register or modify hook succeeds it may update
+ * *for_app_registration_out/_update and must then return 0.
+ * On entry to register, *for_app_registration_out is always NULL.
+ *
+ * A registration or modification hook may fail, in which case it
+ * must leave the registration state of the fd or timeout unchanged.
+ * It may then either return ERROR_OSEVENT_REG_FAIL or any positive
+ * int. The value returned will be passed up through libxl and
+ * eventually returned back to the application. When register
+ * fails, any value stored into *for_registration_out is ignored by
+ * libxl; when modify fails, any changed value stored into
+ * *for_registration_update is honoured by libxl and will be passed
+ * to future modify or deregister calls.
+ *
+ * libxl will only attempt to register one callback for any one fd.
+ * libxl will remember the value stored in *for_app_registration_io
+ * by a successful call to register or modify and pass it into
+ * subsequent calls to modify or deregister.
+ *
+ * register_fd_hooks may be called only once for each libxl_ctx.
+ * libxl may make calls to register/modify/deregister from within
+ * any libxl function (indeed, it will usually call register from
+ * register_event_hooks). Conversely, the application MUST NOT make
+ * the event occurrence calls (libxl_osevent_occurred_*) into libxl
+ * reentrantly from within libxl (for example, from within the
+ * register/modify functions).
+ *
+ * Lock hierarchy: the register/modify/deregister functions may be
+ * called with locks held. These locks (the "libxl internal locks")
+ * are inside the libxl_ctx. Therefore, if those register functions
+ * acquire any locks of their own ("caller register locks") outside
+ * libxl, to avoid deadlock one of the following must hold for each
+ * such caller register lock:
+ * (a) "acquire libxl internal locks before caller register lock":
+ * No libxl function may be called with the caller register
+ * lock held.
+ * (b) "acquire caller register lock before libxl internal locks":
+ * No libxl function may be called _without_ the caller
+ * register lock held.
+ * Of these we would normally recommend (a).
+ *
+ * The value *hooks is not copied and must outlast the libxl_ctx.
+ */
+
+/* It is NOT legal to call _occurred_ reentrantly within any libxl
+ * function. Specifically it is NOT legal to call it from within
+ * a register callback. Conversely, libxl MAY call register/deregister
+ * from within libxl_event_registered_call_*.
+ */
+
+void libxl_osevent_occurred_fd(libxl_ctx *ctx, void *for_libxl,
+ int fd, short events, short revents);
+
+void libxl_osevent_occurred_timeout(libxl_ctx *ctx, void *for_libxl);
+ /* Implicitly, on entry to this function the timeout has been
+ * deregistered. If _occurred_timeout is called, libxl will not
+ * call timeout_deregister; if it wants to requeue the timeout it
+ * will call timeout_register again.
+ */
+
+#endif
+
+/*
+ * Local variables:
+ * mode: C
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index d015c7c..88e7dbb 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -24,6 +24,9 @@
#include <stdlib.h>
#include <string.h>
#include <pthread.h>
+#include <inttypes.h>
+#include <assert.h>
+#include <sys/poll.h>

#include <xs.h>
#include <xenctrl.h>
@@ -91,6 +94,66 @@ _hidden void libxl__log(libxl_ctx *ctx, xentoollog_level msglevel, int errnoval,

/* these functions preserve errno (saving and restoring) */

+typedef struct libxl__gc libxl__gc;
+
+typedef struct libxl__ev_fd libxl__ev_fd;
+typedef void libxl__ev_fd_callback(libxl__gc *gc, libxl__ev_fd *ev,
+ int fd, short events, short revents);
+struct libxl__ev_fd {
+ /* all private for libxl__ev_fd... */
+ LIBXL_LIST_ENTRY(libxl__ev_fd) entry;
+ int fd;
+ short events;
+ int in_beforepolled; /* -1 means not in fd_beforepolled */
+ void *for_app_reg;
+ libxl__ev_fd_callback *func;
+};
+
+
+typedef struct libxl__ev_time libxl__ev_time;
+typedef void libxl__ev_time_callback(libxl__gc *gc, libxl__ev_time *ev,
+ const struct timeval *requested_abs);
+struct libxl__ev_time {
+ /* all private for libxl__ev_time... */
+ int infinite; /* not registered in list or with app if infinite */
+ LIBXL_TAILQ_ENTRY(libxl__ev_time) entry;
+ struct timeval abs;
+ void *for_app_reg;
+ libxl__ev_time_callback *func;
+};
+
+typedef struct libxl__ev_xswatch libxl__ev_xswatch;
+typedef void libxl__ev_xswatch_callback(libxl__gc *gc, libxl__ev_xswatch*,
+ const char *watch_path, const char *event_path);
+struct libxl__ev_xswatch {
+ /* caller should include this in their own struct */
+ /* contents are private to xswatch_register */
+ int slotnum;
+ uint32_t counterval;
+ char *path;
+ libxl__ev_xswatch_callback *callback;
+};
+
+/*
+ * An entry in the watch_slots table is either:
+ * 1. an entry in the free list, ie NULL or pointer to next free list entry
+ * 2. an pointer to a libxl__ev_xswatch
+ *
+ * But we don't want to use unions or type-punning because the
+ * compiler might "prove" that our code is wrong and misoptimise it.
+ *
+ * The rules say that all struct pointers have identical
+ * representation and alignment requirements (C99+TC1+TC2 6.2.5p26) so
+ * what we do is simply declare our array as containing only the free
+ * list pointers, and explicitly convert from and to our actual
+ * xswatch pointers when we store and retrieve them.
+ */
+typedef struct libxl__ev_watch_slot {
+ LIBXL_SLIST_ENTRY(struct libxl__ev_watch_slot) empty;
+} libxl__ev_watch_slot;
+
+libxl__ev_xswatch *libxl__watch_slot_contents(libxl__gc *gc, int slotnum);
+
struct libxl__ctx {
xentoollog_logger *lg;
xc_interface *xch;
@@ -108,6 +171,23 @@ struct libxl__ctx {
* documented in the libxl public interface.
*/

+ int osevent_in_hook;
+ const libxl_osevent_hooks *osevent_hooks;
+ void *osevent_user;
+ /* See the comment for OSEVENT_HOOK_INTERN in libxl_event.c
+ * for restrictions on the use of the osevent fields. */
+
+ int fd_beforepolled_allocd, fd_beforepolled_used;
+ libxl__ev_fd **fd_beforepolled; /* see libxl_osevent_beforepoll */
+ LIBXL_LIST_HEAD(, libxl__ev_fd) efds;
+ LIBXL_TAILQ_HEAD(, libxl__ev_time) etimes;
+
+ libxl__ev_watch_slot *watch_slots;
+ int watch_nslots;
+ LIBXL_SLIST_HEAD(, libxl__ev_watch_slot) watch_freeslots;
+ uint32_t watch_counter; /* helps disambiguate slot reuse */
+ libxl__ev_fd watch_efd;
+
/* for callers who reap children willy-nilly; caller must only
* set this after libxl_init and before any other call - or
* may leave them untouched */
@@ -138,12 +218,12 @@ typedef struct {

#define PRINTF_ATTRIBUTE(x, y) __attribute__((format(printf, x, y)))

-typedef struct {
+struct libxl__gc {
/* mini-GC */
int alloc_maxsize;
void **alloc_ptrs;
libxl_ctx *owner;
-} libxl__gc;
+};

#define LIBXL_INIT_GC(gc,ctx) do{ \
(gc).alloc_maxsize = 0; \
@@ -209,9 +289,137 @@ _hidden char *libxl__xs_read(libxl__gc *gc, xs_transaction_t t,
_hidden char **libxl__xs_directory(libxl__gc *gc, xs_transaction_t t,
const char *path, unsigned int *nb);
/* On error: returns NULL, sets errno (no logging) */
-
_hidden char *libxl__xs_libxl_path(libxl__gc *gc, uint32_t domid);

+
+/*
+ * Event generation functions provided by the libxl event core to the
+ * rest of libxl. Implemented in terms of _beforepoll/_afterpoll
+ * and/or the fd registration machinery, as provided by the
+ * application.
+ *
+ * Semantics are similar to those of the fd and timeout registration
+ * functions provided to libxl_osevent_register_hooks.
+ *
+ * Non-0 returns from libxl__ev_{modify,deregister} have already been
+ * logged by the core and should be returned unmodified to libxl's
+ * caller; NB that they may be valid libxl error codes but they may
+ * also be positive numbers supplied by the caller.
+ *
+ * In each case, there is a libxl__ev_FOO structure which can be in
+ * one of three states:
+ *
+ * Undefined - Might contain anything. All-bits-zero is
+ * an undefined state.
+ *
+ * Idle - Struct contents are defined enough to pass to any
+ * libxl__ev_FOO function but not registered and
+ * callback will not be called. The struct does not
+ * contain references to any allocated resources so
+ * can be thrown away.
+ *
+ * Active - Request for events has been registered and events
+ * may be generated. _deregister must be called to
+ * reclaim resources.
+ *
+ * These functions are provided for each kind of event KIND:
+ *
+ * int libxl__ev_KIND_register(libxl__gc *gc, libxl__ev_KIND *GEN,
+ * libxl__ev_KIND_callback *FUNC,
+ * DETAILS);
+ * On entry *GEN must be in state Undefined or Idle.
+ * Returns a libxl error code; on error return *GEN is Idle.
+ * On successful return *GEN is Active and FUNC wil be
+ * called by the event machinery in future. FUNC will
+ * not be called from within the call to _register.
+ *
+ * void libxl__ev_KIND_deregister(libxl__gc *gc, libxl__ev_KIND *GEN_upd);
+ * On entry *GEN must be in state Active or Idle.
+ * On return it is Idle. (Idempotent.)
+ *
+ * void libxl__ev_KIND_init(libxl__ev_KIND *GEN);
+ * Provided for initialising an Undefined KIND.
+ * On entry *GEN must be in state Idle or Undefined.
+ * On return it is Idle. (Idempotent.)
+ *
+ * int libxl__ev_KIND_isregistered(const libxl__ev_KIND *GEN);
+ * On entry *GEN must be Idle or Active.
+ * Returns nonzero if it is Active, zero otherwise.
+ * Cannot fail.
+ *
+ * int libxl__ev_KiND_modify(libxl__gc*, libxl__ev_KIND *GEN,
+ * DETAILS);
+ * Only provided for some kinds of generator.
+ * On entry *GEN must be Active and on return, whether successful
+ * or not, it will be Active.
+ * Returns a libxl error code; on error the modification
+ * is not effective.
+ *
+ * All of these functions are fully threadsafe and may be called by
+ * general code in libxl even from within event callback FUNCs.
+ */
+
+
+_hidden int libxl__ev_fd_register(libxl__gc*, libxl__ev_fd *ev_out,
+ libxl__ev_fd_callback*,
+ int fd, short events /* as for poll(2) */);
+_hidden int libxl__ev_fd_modify(libxl__gc*, libxl__ev_fd *ev,
+ short events);
+_hidden void libxl__ev_fd_deregister(libxl__gc*, libxl__ev_fd *ev);
+static inline void libxl__ev_fd_init(libxl__ev_fd *efd)
+ { efd->fd = -1; }
+static inline int libxl__ev_fd_isregistered(libxl__ev_fd *efd)
+ { return efd->fd >= 0; }
+
+_hidden int libxl__ev_time_register_rel(libxl__gc*, libxl__ev_time *ev_out,
+ libxl__ev_time_callback*,
+ int milliseconds /* as for poll(2) */);
+_hidden int libxl__ev_time_register_abs(libxl__gc*, libxl__ev_time *ev_out,
+ libxl__ev_time_callback*,
+ struct timeval);
+_hidden int libxl__ev_time_modify_rel(libxl__gc*, libxl__ev_time *ev,
+ int milliseconds /* as for poll(2) */);
+_hidden int libxl__ev_time_modify_abs(libxl__gc*, libxl__ev_time *ev,
+ struct timeval);
+_hidden void libxl__ev_time_deregister(libxl__gc*, libxl__ev_time *ev);
+static inline void libxl__ev_time_init(libxl__ev_time *ev)
+ { ev->func = 0; }
+static inline int libxl__ev_time_isregistered(libxl__ev_time *ev)
+ { return !!ev->func; }
+
+
+_hidden int libxl__ev_xswatch_register(libxl__gc*, libxl__ev_xswatch *xsw_out,
+ libxl__ev_xswatch_callback*,
+ const char *path /* copied */);
+_hidden void libxl__ev_xswatch_deregister(libxl__gc *gc, libxl__ev_xswatch*);
+
+static inline void libxl__ev_xswatch_init(libxl__ev_xswatch *xswatch_out)
+ { xswatch_out->slotnum = -1; }
+static inline int libxl__ev_xswatch_isregistered(const libxl__ev_xswatch *xw)
+ { return xw->slotnum >= 0; }
+
+
+
+_hidden void libxl__event_disaster(libxl__gc*, const char *msg, int errnoval,
+ libxl_event_type type /* may be 0 */,
+ const char *file, int line,
+ const char *func);
+ /*
+ * In general, call this via the macro LIBXL__EVENT_DISASTER.
+ *
+ * Event-generating functions may call this if they might have
+ * wanted to generate an event (either an internal one ie a
+ * libxl__ev_FOO_callback or an application event), but are
+ * prevented from doing so due to eg lack of memory.
+ *
+ * NB that this function may return and the caller isn't supposed to
+ * then crash, although it may fail (and henceforth leave things in
+ * a state where many or all calls fail).
+ */
+#define LIBXL__EVENT_DISASTER(gc, msg, errnoval, type) \
+ libxl__event_disaster(gc, msg, errnoval, type, __FILE__, __LINE__, __func__)
+
+
/* from xl_dom */
_hidden libxl_domain_type libxl__domain_type(libxl__gc *gc, uint32_t domid);
_hidden int libxl__domain_shutdown_reason(libxl__gc *gc, uint32_t domid);
@@ -536,6 +744,8 @@ _hidden int libxl__parse_mac(const char *s, libxl_mac mac);
/* compare mac address @a and @b. 0 if the same, -ve if a<b and +ve if a>b */
_hidden int libxl__compare_macs(libxl_mac *a, libxl_mac *b);

+_hidden int libxl__gettimeofday(libxl__gc *gc, struct timeval *now_r);
+
#define STRINGIFY(x) #x
#define TOSTRING(x) STRINGIFY(x)

--
1.7.2.5


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